Crankshaft supporting arrangement for internal combustion engines



Feb. 14, 1967 D. c. AL N 3,304,134

CRANKSHAFT SUPPORTING ARR GEMEN'I FOR INTERNAL COMBUSTION ENGINES Filed May 26, 1964 IN VENTOR.

ATTORNEY United States Patent 3,304 134 CRANKSHAFT SUPPGRTING ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES Donald C. Allen, Dearborn, Mich., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed May 26, 1964, Ser. No. 370,312 7 Claims. (Cl. 308-23) This invention relates to internal combustion engines and, more particularly, to the cylinder block and crankshaft supporting portions thereof.

Specifically, the invention contemplates an improved crankshaft supporting arrangement including a resilient bridge member which is effective to reduce the cyclic stresses at the main bearing seat area by transferring a substantial portion of tensile loads normally imposed by the main bearing cap retaining means from the bearing seat area to the adjacent side Walls of the cylinder block. The invention thereby permits the reduction of main bearing web size from what would otherwise be required for a given main bearing load or, alternatively, the substitution of lower strength materials in the bearing web may be permitted without substantially changing the engine design. For example, such an arrangement has made possible substitution of aluminum as the cylinder block material in place of cast iron without a reduction in the engine rated output where such a reduction would have otherwise been required.

Further objects and advantages of the invention will be apparent from the following description and drawings in which:

FIGURE 1 is a side elevational view partially in crosssection of an engine embodying the invention; and

FIGURE 2 is a cross-sectional view of the engine of FIGURE 1 taken generally along the plane indicated at 2-2.

Referring now to the drawings, there is shown in FIG- URE 1 an engine generally indicated by numeral 10 having a cylinder block 12, the lower portion of which defines a crankcase cavity 14 in which is rotatably carried a crankshaft 16. The crankshaft includes a plurality of main journals 18 longitudinally spaced along its length, between which are located eccentric throws 20, carrying the lower ends of connecting rods 22. The connecting rods are connected at their upper ends with the usual pistons (not shown) which are reciprocable in their respective cylinders (not shown) of the cylinder block 12.

Referring now to FIGURE 2, the lower portion of cylinder block 12 includes two longitudinally extending spaced side walls which partially define crankcase cavity 14. Extending transversely across the crankcase cavity 14 and in lateral alignment with each crankshaft journal 18 is a web or bulkhead 32 which connects with opposite side walls 30 and may be integrally formed therewith. Centrally located at the lower edge of each web 32 is a semi cylindrical bearing recess 34 which is adapted to receive the upper of a pair of main bearing shells '36 and 38 in which the respective crankshaft journal 18 is retained.

Adjacent each side of bearing recess 34 is a horizontal machined face 40 against which the legs of a main bearing cap 42 are retained, thereby securing lower bearing shell 38 in place beneath journal 18. Bearing cap 42 may additionally be provided with vertical shoulders 44 which are attached to fit closely between complementary vertical shoulders 46 formed in web 32 which serves to transversely position the bearing cap with respect to cylinder block 12. A pair of drilled holes 48 are provided, one extending through each leg of main bearing cap 42, and are adapted to receive securing means such as studs ice 50 which are threaded into complementary tapped holes 52 in web 32.

In conventional engine construction, nuts would be placed on the outer ends of studs 50 in engagement with main bearing cap 42 thereby directly securing the cap to web 32. As a consequence, the combustion and reciprocating forces carried by main bearing cap 42 would be transferred entirely to studs 50, requiring the metal surrounding tapped holes 52 to absorb relatively high tensile stresses While the metal immediately therebelow adjacent surface 40 is exposed to high compressive stresses. In order to withstand these stresses, in what may be termed the main bearing seat area, a relatively sturdy web construction is called for and a relatively high strength material, such as cast iron, is commonly used.

There are occasions, however, when it is desirable to reduce the thickness of the main bearing web structure in order to produce a more compact engine. In addition, it is sometimes advantageous to produce an engine having an aluminum block from a design and on tooling intended for a cast iron block engine. Such an engine may be made lighter in weight and, therefore, would have an advantage for some purposes if the rated output could be maintained at a substantially high level. Unfortunately, the change to thinner wall sections in the crank case web, or the substitution of aluminum for cast iron in such a construction, would result in a lessening of the ability to absorb stresses in the main bearing seat area.

In order to accomplish such design changes as those above suggested without substantially reducing the rated output, of which an engine would be otherwise capable, the

present invention introduces an additional load carrying,

structure in the form of a bridge support 60. This member comprises a resilient metal beam which is arranged to extend underneath bearing cap 42 and outwardly into overlapping spaced relation with the adjacent lower faces 62 of side walls 30. Projecting bosses 64 are provided which engage laterally spaced seats 66 formed on the lower faces of bearing cap 42 surrounding holes 48, and complementary holes 68 are drilled through support 60 to receive the ends of studs 50. Member 60 is retained in engagement with bearing cap 42 by the application of nuts 70 to the ends of studs 50 and this construction thereby retains bearing cap 42 against web 32.

The outer ends 72 of support 60 include finished surfaces 74 which are adapted to engage lower faces 62 of the respective side walls 30. Furthermore, ends 72 are provided with drilled holes 76 through which additional stud members 78 extend from complementary recessed tapped holes 80 located in the side walls 30 of cylinder block 12.. The depth of recessed holes 80 is completely a function of the engine structure, the threaded portion of the holes being located at a point in the side walls at which maximum stress concentration will be acceptable. Nuts 82 are provided at the outer ends of studs 78 to force support ends 72 toward side walls 30.

The construction of the bridge support 69 is such that before nuts 82 are tightened, a predetermined clearance 84 exists between the surfaces 74 of the support ends and lower faces 62 of the side walls. Upon tightening of nuts 82 a sufficient torque value, support member 61) is caused to bend until clearance 84 is closed and finished surfaces 74 come into contact with lower faces 62. This causes a predetermined force to be exerted by bosses 64 on bearing cap 42 increasing the force with which it is held in its position against web 32 without adding to the tensile stresses in the main bearing seat area. The stresses accounting for the additional force are, in effect, transferred to the side walls in the area of tapped holes 80 which are a much less critical area than the main bearing seat area around tapped holes 52 and machined faces 40. It should be understood that more or less stress can be transferred from the main bearing seat area to the side walls as may be required by the demands of the particular situation.

The force exerted by a particular bridge support member is dependent upon a number of variables including those of the structure and material of which the support member is formed and the dimensional relationships existing with the associated engine components. Of par ticular importance is the amount of clearance 84 which is provided in the untightened state between the finished surfaces 74 at the outer ends of the support member and the lower faces 62 of the side walls. The amount of this clearance can, of course, be varied as desired but it is limited by reasonable manufacturing tolerances and the bending yield strength of the bridge support member.

It should now be clear that the present invention has provided a structure which is effective to transfer a desired portion of cylinder block stresses, occasioned by retention thereon of a main bearing cap, from the critical main bearing seat area to the less critical side walls of an engine cylinder block, which thereby allows the use of lighter and lower strength materials in the block for equivalent main bearing loads or allows the use of smaller cross-sectional areas in the main bearing webs.

The invention provides the additional advantage of lending lateral and longitudinal support to the main bearing caps by connecting the outer ends of the caps with the lower edge of their associated cylinder block side walls. In this regard, the invention is similar to certain embodiments of the construction shown in United States Patent 3,046,954, Hoffman et al., which is applicable to engines of the general type shown herein. The present invention is unique, however, in providing an arrangement capable of reducing stresses in the main bearing seat area by transferring a portion of the main bearing cap securing forces to the cylinder block side Walls.

It will be obvious to those skilled in the art that various changes might be made in the invention as disclosed without departing from its spirit and scope as defined in the following claims.

What is claimed is:

1. Crankshaft supporting means comprising;

a block having a crankshaft receiving portion;

a crankshaft retaining cap engaging the block on op- .posite sides of and adjacent the crankshaft receiving portion;

securing means engaging the block adjacent the crankshaft receiving portion and exerting a force holding the cap against the block;

a resilient beam extending between and secured to,

spaced portions of the block outboard of the cap and clamped against the cap at a point generally between the spaced portions; and

means resiliently deforming said beam so as to exert an additional force on said cap additive to that of said securing means to thereby assist in holding the cap in engagement with the block.

2. In an internal combustion engine, crankshaft supporting means comprising;

a cylinder block having spaced side walls, said cylinder block having at least one transverse web extending between the side walls and including a crankshaft receiving portion;

:a crankshaft retaining cap held against the web and supporting a crankshaft between the side walls and in the crankshaft receiving portion;

securing means engaging the web on opposite sides of and adjacent the crankshaft receiving portion, said securing means exerting a positive force holding the cap against the web;

a resilient beam extending between and secured to the side walls and engaging the cap at a point generally between the side walls; and

means resiliently deforming said beam so as to exert an additional force on said cap additive to that of said securing means to thereby assist in holding the cap in engagement with the block.

3. In an internal combustion engine, crankshaft supporting means comprising:

a cylinder block having two spaced and longitudinally extending side walls, said cylinder block having at least one crankshaft supporting web extending transversely between the side walls;

a crankshaft supporting cap member, mateable with the web;

a resilient bridge support member extending transversely into overlapping spaced relation with the side walls and including means mateable with the cap member, said bridge support member maintaining in the undeformed condition a predetermined clearancefrom the side walls; and

means secured to the side walls and bending the bridge support member into engagement therewith, causing a predetermined seating force to be exerted on the cap member.

4. In the combination set forth in claim 3, securing means engaging the web and exerting a positive force holding the cap member against the web, the holding force exerted on the cap by the securing means being less than the total force holding the cap in engagement with the web.

5. In an internal combustion engine of the type hava cylinder block including spaced side walls and at least one transverse web extending between the side walls, such transverse web having a crankshaft receiving portion therein;

a main bearing cap engaging the web and retaining a crankshaft between the side walls and in the crankshaft receiving portion; and

stressed securing means engaging the web, adjacent the crankshaft receiving portion, and urging the main bearing cap thereagainst; the improvement com-prisin g means for apportioning the main bearing cap seating loads between the web, adjacent the crankshaft receiving portion, and the side walls, said apportioning means including a resilient bridge support secured to and extending between the side walls and engaging the main bearing cap threbetween and means, resiliently deforming said bridge support so as to assist in urging the main bearing cap against the web.

6. In an internal combustion engine, crankshaft supporting means comprising;

a cylinder block having two spaced and longitudinally extending side walls;

said cylinder block including a plurality of crankshaft supporting webs, spaced longitudinally and extending transversely between the side walls, each such web having a hemispherical crankshaft receiving portion and adjacent thereto a pair of diametrically disposed laterally spaced surfaces, each surface surrounding .one of a pair of threaded holes formed in the web;

a plurality of crankshaft supporting cap members, each engaging the respective laterally spaced surfaces of an associated one of the webs and including a pair of drilled holes aligned with the threaded holes of the web, each cap member further including at its outer surface a pair of laterally spaced seats, each seat surrounding one of the pair of drilled holes;

a plurality of resilient bridge support member each having portions extending transversely into overlapping relation with the side walls, each such support member being matea ble with an associated one of the cap members and including a pair of laterally spaced bosses engaging the corresponding pair of laterally spaced seats of the associated cap member and a pair of drilled holes aligned with the holes in the associated cap member;

a first pair of threaded securing means retained in each pair of threaded holes of the web and extending through the aligned holes in each associated cap member and bridge support member whereby to exert a positive force retaining these members in assembled relation and seating each bearing cap against its associated web;

each said bridge support member further including a pair of finished surfaces, one formed on each portion of the bridge support overlapping the respective side walls and in predetermined spaced relation therewith, and a pair of drilled openings associated one with each finished surface;

said side walls being provided With a plurality of pairs of recessed threaded holes, one pair aligned with the drilled openings of each bridge support member; and

a second pair of threaded securing means retained in each pair of recessed threaded holes and extending through the respective drilled Openings of each bridge support member, said second securing means being adapted to bend the associated bridge support member, causing the finished surfaces to engage the respective side walls and resulting in a predetermined seating force being exerted on each bearing cap by the associated bridge support member;

whereby the seating force exerted by each said first pair of threaded securing means is less than the total seat ing force exerted on each associated bearing cap.

7. In an internal combustion engine, crankshaft supporting means comprising;

a cylinder block having two spaced and longitudinally extending side walls, said cylinder block having at least one crankshaft supporting web extending transversely between the side Walls:

a crankshaft supporting cap member, mateable with the web;

a resilient bridge support member extending transversely into overlapping spaced relation with the side walls and including means mateable with the cap member, said bridge support member maintaining in the undeformed condition a predetermined clearance from the side walls;

means secured to the side walls and bending the bridge support member into engagement therewith, causing a predetermined seating force to be exerted on the cap member; and

additional means through said bridge support member and said cap and secured in said web, said additional means urging said bridge support member into engagement with said cap member thereby causing an additional seating force to be exerted by said bridge support member on said cap member above the said predetermined seating force caused by the bending of said bridge support member into engagement with said side walls.

References Cited by the Examiner UNITED STATES PATENTS 1,909,977 5/1933 Miller 30823 3,046,954 7/1962 Hoffman et al. 92-149 FOREIGN PATENTS 506,149 9/1954 Canada. 118,371 8/1918 Great Britain.

MARTIN P. SCHWADRON, Primary Examiner.

DAVID J. WILLIAMOWSKY, Examiner.

N. ABRAMS, R. F. HESS, Assistant Examiners. 

1. CRANKSHAFT SUPPORTING MEANS COMPRISING; A BLOCK HAVING A CRANKSHAFT RECEIVING PORTION; A CRANKSHAFT RETAINING CAP ENGAGING THE BLOCK ON OPPOSITE SIDES OF AND ADJACENT THE CRANKSHAFT RECEIVING PORTION; SECURING MEANS ENGAGING THE BLOCK ADJACENT THE CRANKSHAFT RECEIVING PORTION AND EXERTING A FORCE HOLDING THE CAP AGAINST THE BLOCK; A RESILIENT BEAM EXTENDING BETWEEN AND SECURED TO SPACED PORTIONS OF THE BLOCK OUTBOARD OF THE CAP AND CLAMPED AGAINST THE CAP AT A POINT GENERALLY BETWEEN THE SPACED PORTIONS; AND 